The present invention relates to a step up transformer used to supply energy to a miniaturized x-ray source located in an x-ray catheter by stepping up the voltage at the distal end of the catheter to provide the high voltage, e.g. 10,000-60,000 volts. Such high voltages are needed to accelerate electrons to create x-rays necessary for the intended therapeutic use. The step up transformer allows transmission of a lower voltage down the length of the x-ray catheter than would otherwise be necessary, allowing for safer operation of the x-ray device by minimizing hazards to both operator and patient.
Traditionally, x-rays have been used in the medical industry to view bone, tissue and teeth. X-rays have also been used to treat cancerous and precancerous conditions by exposing a patient to x-rays using an external x-ray source. Treatment of cancer with x-rays presents many well documented side effects, many of which are due to the broad exposure of the patient to the therapeutic x-rays.
Minimally invasive endoscopic techniques have been developed and are used to treat a variety of conditions. Endoluminal procedures are procedures performed with an endoscope, a tubular device into the lumen of which may be inserted a variety of rigid or flexible tools to treat or diagnose a patient""s condition.
The desire for improved minimally invasive medical devices and techniques have led to the development of miniaturized x-ray devices that may be used in the treatment or prevention of a variety of medical conditions. International Publication No. WO 98/48899 discloses a miniature x-ray unit having an anode and cathode separated by a vacuum gap positioned inside a metal housing. The anode includes a base portion and a projecting portion. The x-ray unit is insulated and connected to a coaxial cable which, in turn, is connected to the power source. An x-ray window surrounds the projecting portion of the anode and the cathode so that the x-rays can exit the unit. The x-ray unit is sized for intra-vascular insertion, and may be used, inter alia, in vascular brachytherapy of coronary arteries, particularly after balloon angioplasty.
International Publication No. WO 97/07740 discloses an x-ray catheter having a catheter shaft with an x-ray unit attached to the distal end of the catheter shaft. The x-ray unit comprises an anode and a cathode coupled to an insulator to define a vacuum chamber. The x-ray unit is coupled to a voltage source via a coaxial cable. The x-ray unit can have a diameter of less than 4 mm and a length of less than about 15 mm, and can be used in conjunction with coronary angioplasty to prevent restenosis.
One difficulty encountered in miniaturized x-ray technology is generating the amount of voltage necessary to produce x-ray source while located inside the body. In other applications, transformers have been used to assist generating the required voltages. For example, U.S. Pat. No. 4,652,846 discloses a transformer of small installed volume, which affords, besides electrical separation, an effective static protective shield between the power supply side and the user side, along with simple production and assembly. To accomplish this, a two-chamber transformer with a coil formed for the primary winding and a coil formed for the secondary winding is used. Both are plugged one behind the other onto the transformer core in the direction of the coil axes and a stamped metal foil frame is used as a shielding wall between the adjacent face flanges of the coil forms used. The transformer is particularly well suited for application in equipment of the entertainment, communications and medical technologies.
U.S. Pat. No. 5,793,272 discloses a high quality factor (Q) spiral and toroidal inductor and transformer that are compatible with silicon Very Large Scale Integrations (VLSI) processing, which consume a small IC and operate at high frequencies. The spiral inductor has a spiral metal coil deposited in a trench formed in an dielectric layer over a substrate. The metal coil is enclosed in ferromagnetic liner and capped layers, and is connected to an underpass contact through a metal filled via in the dielectric layer. The spiral inductor also includes ferromagnetic coil lines surrounded by the metal spiral coil. A spiral transformer is formed by vertically stacking the two spiral inductors, while placing them side by side over a ferromagnetic bridge formed below the metal coils and core lines. The toroidal inductor includes a toroidal metal coil with a core having ferromagnetic strips. The toroidal metal coil is segmented into two coils, each having a pair of ports to form a toroidal transformer.
The present invention provides a step up transformer that overcomes difficulties associated with generating sufficient energy to generate x-rays in a miniaturized x-ray source.
The present invention relates in part to a step-up transformer capable of boosting voltage from a power source to at least 100 times, and preferably at least 1000 times, the voltage of the power input. The transformer includes primary electrically conductive windings surrounding a non-electrically conductive core. Secondary windings surround the primary windings, preferably in a ratio of 1000:1. The transformer is compact, e.g., from 2 to 25 mm and are particularly suited for use with x-ray catheters that generate x-rays at a power source when placed inside the body of a patient.
The present invention also relates to x-ray catheters having the step-up transformer. The x-ray catheter will include an x-ray emitter source, which typically will comprise an anode/cathode arrangement inside a vacuum tube, which is operably connected to a power source. The transformer is operably connected to the power source, and increases the voltage from the power source to a voltage sufficient to generate x-rays at the x-ray emitter source.
Methods of treating patients with the device are also a feature of the invention.